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Factorizations of properties of graphs

Izak Broere, Samuel John Teboho Moagi, Peter Mihók, Roman Vasky (1999)

Discussiones Mathematicae Graph Theory

A property of graphs is any isomorphism closed class of simple graphs. For given properties of graphs ₁,₂,...,ₙ a vertex (₁, ₂, ...,ₙ)-partition of a graph G is a partition V₁,V₂,...,Vₙ of V(G) such that for each i = 1,2,...,n the induced subgraph G [ V i ] has property i . The class of all graphs having a vertex (₁, ₂, ...,ₙ)-partition is denoted by ₁∘₂∘...∘ₙ. A property is said to be reducible with respect to a lattice of properties of graphs if there are n ≥ 2 properties ₁,₂,...,ₙ ∈ such that = ₁∘₂∘...∘ₙ;...

Fair majorities in proportional voting

František Turnovec (2013)

Kybernetika

In parliaments elected by proportional systems the seats are allocated to the elected political parties roughly proportionally to the shares of votes for the party lists. Assuming that members of the parliament representing the same party are voting together, it has sense to require that distribution of the influence of the parties in parliamentary decision making is proportional to the distribution of seats. There exist measures (so called voting power indices) reflecting an ability of each party...

Fall coloring of graphs I

Rangaswami Balakrishnan, T. Kavaskar (2010)

Discussiones Mathematicae Graph Theory

A fall coloring of a graph G is a proper coloring of the vertex set of G such that every vertex of G is a color dominating vertex in G (that is, it has at least one neighbor in each of the other color classes). The fall coloring number χ f ( G ) of G is the minimum size of a fall color partition of G (when it exists). Trivially, for any graph G, χ ( G ) χ f ( G ) . In this paper, we show the existence of an infinite family of graphs G with prescribed values for χ(G) and χ f ( G ) . We also obtain the smallest non-fall colorable...

Families of strongly projective graphs

Benoit Larose (2002)

Discussiones Mathematicae Graph Theory

We give several characterisations of strongly projective graphs which generalise in many respects odd cycles and complete graphs [7]. We prove that all known families of projective graphs contain only strongly projective graphs, including complete graphs, odd cycles, Kneser graphs and non-bipartite distance-transitive graphs of diameter d ≥ 3.

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